docs: def check_impl(self):
          """
          Overridden to open the left and right zipfiles and to provide all
          subchecks with an open ZipFile instance rather than having
          them all open and close the ZipFile individually. For the
          duration of the check (which calls collect_impl), the
          attributes self.lzip and self.rzip will be available and used
          as the ldata and rdata of all subchecks.
          """
  
          with open_zip(self.ldata) as lzip:
              with open_zip(self.rdata) as rzip:
                  self.lzip = lzip
                  self.rzip = rzip
                  ret = super(JarContentsChange, self).check_impl()
  
          self.lzip = None
          self.rzip = None
  
          return ret